A fan conventionally used in an air conditioner is disclosed, for example, in Japanese Laid-open Utility Model No. 54-20004. This Japanese Laid-open Utility Model No. 54-20004 relates to a fan integrally forming blades and an end plate, and this fan is formed of a mixture of acrylonitrile styrene resin (AS resin), and about 20 wt. % to about 40 wt. % of glass fiber (GF). The mechanical strength is improved by mixing glass fiber. Generally, the synthetic resin end plate and blades are integrally bonded by ultrasonic fusion, and then molding strain and strain by ultrasonic fusion are removed by annealing treatment by circulation of hot air of about 80 to 95.degree. C. in a hot air circulating oven or the like. By such treatment, the heat and creep resistance is enhanced as the fan in actual use.
Annealing is a treatment for removing strain. However, in the constitution of such conventional fan, in order to enhance the mechanical strength of the molding, the annealing treatment for removing fusion strain or molding strain after processing by ultrasonic fusion of end plate and blades by mixing about 20 to 40 wt. % of GF in the AS resin as synthetic resin material is done in an ordinary annealing oven having a temperature difference of 5.degree. C. or more between the top and bottom of the fan, and the circulation of hot air is at wind velocity of 0.5 m/sec or less. Hence, it required a long time in annealing the entire fan uniformly. This method was therefore inferior in productivity and processability. Moreover, such synthetic resin material is inferior in flowability, short shots are likely to occur when molding, and, as a result, the yield and productivity were inferior.
It is hence an object of the invention to present a fan free from fusion strain and molding strain, and excellent in molding performance, rigidity, impact resistance, heat and creep resistance, and productivity.